1. Field of the Invention
The invention pertains to the field of bar and c-clamp type tools used for holding two or more workpieces at fixed angles to each other. More particularly, the invention pertains to an improvement to clamps to allow two or more clamps to be joined at fixed angles to each other while they hold a workpiece or workpieces.
2. Description of Related Art
Bar clamps, C-clamps, and related tools, typically exert their force along one line. While much prior art has been devoted to immobilization of workpieces and clamps relative to the plane of the workpieces, there has been little work done in joining bar or c-clamps rigidly in a manner that allows them to exert force on a joint along multiple lines. Clamping at right angles to another bar clamp is usually done with the geometry of the second clamp being unfixed relative to the first clamp. Further, special jigs are needed to maintain multiple clamps parallel to each other in situations where such precision is desired.
Numerous systems have been developed to create “universal” clamps that allow clamping along more than one axis (U.S. Pat. No. 4,125,251), to clamp at right angles to a frame (U.S. Pat. No. 6,491,294), and to interconnect c-clamps for building complex clamping jigs (U.S. Pat. No. 4,747,590). Miter clamps and strap clamps have been developed to allow additional clamping geometries. Each approach has a weakness. Some do not allow assembly of interconnecting clamps on more than one plane, or require threaded bar stock to do so, with commensurately longer setup time. Some systems are comprised of specially made clamping blocks that are not useful without other components. Some are specialized for one joint type and are useless for clamping other joints. Many of these specialized clamps are not useful for basic clamping tasks that bar and c-clamps are used for.
In addition to variations on bar and c-clamps, there are a large number of clamping “systems” that are designed to be used for a wide variety of clamping situations. These systems may be for 2-dimensional clamping tasks, such as U.S. Pat. No. 4,125,251, which fixes clamped objects on a table, or complicated 3-dimensional clamping tasks, such as U.S. Pat. No. 3,883,128 and U.S. Pat. Nos. 4,747,590 and 4,753,425. Some clamp systems such as the latter use threaded connectors between clamps, which have the advantage of strongly fixing the distance between clamps at the cost of time-consuming setup.
To allow clamps to be quickly used in unison with one another while maintaining their individual usefulness, c-clamps have been developed that join at the bar connecting their jaws, as in U.S. Pat. No. 2,636,527, miter clamps have been developed that can pivot on a rod through the bar connecting their jaws, as in U.S. Pat. No. 994630, and clamps that can pivot on a rod through the bar connecting their jaws, capable of maintaining fixed angles, as in U.S. Pat. No. 1,352,647. These designs generally cannot interlock the component clamps in such a way as to permit multiple clamps to act in parallel on a large, flat workpieces, such as is often required in cabinetmaking.
This defect is not shared by U.S. Pat. No. 4,607,829 which comprises c-clamps with two holes on each jaw as well as the (fixed) bar that connects the jaws. These holes are aligned so as to allow the clamps to be fastened together in a variety of configurations, including in parallel and at fixed 90 or 45 degree angles to a flat workpiece. U.S. Pat. No. 4,607,829 does not, however, include any mechanism to lock or vary the angle of the clamping axes other than that provided by the two fasteners joining adjacent clamps and the fixed geometry of the clamp bodies, and requires a spacer or shim to join clamps in parallel at a distance from each other along the connecting bolts. In addition, there is no provision for the use of f-clamps with this mechanism.